Solar membrane distillation: A control perspective

Abstract

Abstract-This paper presents a preliminary architecture for controlling solar membrane distillation facilities. Membrane distillation (MD) is a desalination technology under investigation, without industrial applications and with only few pilot systems. There is a general lack of information on how these systems perform during real solar-powered operation and how distillate quality deteriorates under intermittent conditions. One of the few systems that have been fully described in literature is the MD-solar pilot plant in Plataforma Solar de Almería (PSA), Spain. This paper presents a first step towards an optimal automatic operation of this system through the definition of operation modes and basic control loops. A discussion of control schemes to be implemented in the near future is also included in this work.

Using a Nonlinear Model Predictive Control strategy for the efficient operation of a solar-powered membrane distillation system

“…The model of the heat generation circuit was already presented and validated in [11], [12], [14]. This model includes a lumped-parameters model of the solar field according to [15], a stratified model of the storage tank based on an energy balance [16], and a first principles-based model of the heat exchanger [17].…”

“…The direct control layer is composed by five loops and it was developed and tested in [11], [12], [14]. As it has been pointed out before, the objective of this control layer is to maintain near steady state conditions the main variables involved in the process.…”

A feedback control system with reference governor for a solar membrane distillation pilot facility

“…Therefore, different kinds of modules and Membrane Distillation (MD) configurations have been evaluated in the recent years in terms of thermal efficiency and distillate production [7,8]. The experimental campaigns carried out in these studies require steady state conditions in the main process variables in spite of changes in the energy source (solar radiation), thus demanding adequate control systems to achieve desired performance [9].…”

Optimal operation of a Solar Membrane Distillation pilot plant via Nonlinear Model Predictive Control

“…The facility is also equipped with a thermal storage tank (1500 L) that is used as energy buffer device to store and manage the thermal energy coming from the solar field. The storage tank permits the operation of the plant in several modes, as it was described in Gil et al (2015a). In this paper the MD module is fed by the storage tank, 120 which is heated by recirculating the fluid through the solar field (see Section 2.3).…”

“…As it has been highlighted before, the SMD plant can be operated in different modes (Gil et al, 2015a). In this case, the fluid coming from the solar field flows directly to the tank, which is used to feed the module.…”